Various techniques are known in the art of forming a conductive material over a substrate during fabrication of devices in integrated circuitry. Such techniques include atomic layer deposition (ALD), chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition (PECVD), and other known deposition processes. ALD, CVD, PECVD, and other thin film deposition processes use volatile precursors to form conductive materials of a desired chemical composition on a substrate surface.
Often, the conductive material to be formed is a metal, metal oxide, or a metal nitride material. There may be several possible methods of forming such a material with a particular chemical composition on a substrate surface, however, each method may result in different physical or chemical properties of the as-deposited material. Varying deposition conditions, such as deposition temperature or precursors, may alter the capacitance, leakage current, resistance, or breakdown voltage of the as-deposited material. For instance, using a halogen-containing metal precursor, such as titanium tetrachloride (TiCl4), to form the conductive material may result in damage to underlying materials upon which the conductive material is formed. The halogen-containing metal precursor reacts with the underlying material, such as a high-k dielectric material, causing an interface between the conductive material and the underlying material to be damaged before the conductive material coalesces. For example, when forming a titanium nitride (TiN) material using TiCl4 over a high-k dielectric material, the TiCl4 may react with the high-k dielectric material and form a discontinuous (e.g., non-uniform) titanium oxide and titanium suboxide material between the high-k dielectric material and the TiN material. This discontinuous titanium oxide and titanium suboxide may cause increased leakage current through the dielectric material and may introduce localized micro roughness and state density at the interface between the conductive material and the underlying high-k dielectric material, leading to lower capacitance of a semiconductor device that includes the high-k dielectric material.
Despite these disadvantages, some of these halogen-containing metal precursors exhibit beneficial properties, such as high capacitance of the resulting stack structure. Various solutions have been attempted to overcome these problems including increasing the thickness of the underlying materials to effectively block leakage current, forming the conductive materials with organic precursors, or forming the conductive material at lower process temperatures. However, each of these solutions creates problems such as increased equivalent oxide thickness or a decrease in overall capacitance of the stack structure.
It would be desirable to form a conductive material to increase the overall device capacitance without damaging or etching underlying material or materials. It would also be desirable to form the conductive material using a halogen-containing metal precursor.